In the parent application, an apparatus is disclosed which provides improved mud wiping in a tubing string. The apparatus shown in the referenced parent application is intended to wipe the mud clinging to the wall of a drill string when the drill string is pulled from the well. This typically occurs at the time a drill bit is changed. For example, the drill bit may wear out when the drill string is about 10,000 feet long. This necessitates pulling the drill pipe in stands of about ninety feet each. As each stand of pipe is pulled from the bore, the drill bit is pulled closer to the surface as the drill string is disassembled. Disassembly of the drill string above the rotary table, as is customary, results in spilling some mud on the floor from the stand of pipe just pulled from the well. The apparatus shown in the parent application is directed to a device which wipes the mud away from the wall and forces it downwardly. The device in effect floats on top of the column of mud standing in the drill string. As it is wiped away, the column falls relatively in the drill string. The drill string is pulled upwardly relative to the apparatus. The apparatus includes pressure responsive means which causes it to set in the event a blow-out is directed up the drill string.
The referenced disclosure includes various wiping elements. While they have met with some success, the improvement of the present disclosure clearly provides improved operation. The apparatus has a wiping lip which is opened downwardly to force mud under the lip, causing it to swell or expand. When it swells, it flares outwardly against the side wall of the surrounding pipe. This is good for internal flush drill pipe. Normally drill pipe is formed with reinforced couplings between joints. Each joint is assembled by threading together a pin and box. The pin and box are reinforced by fabrication of a coupling which has a thick construction. This forms an upset in the pipe which must be on the interior or exterior of the pipe. The upset is often placed on the exterior where it forms no problem. However, internal upset pipe presents some problems in clean wiping. The apparatus of the present invention overcomes problems with wiping the interior of a pipe when there are internal upsets.